Feeling unusually tired, gaining or losing weight without an obvious reason, becoming unusually sensitive to cold or heat, experiencing hair changes, or noticing changes in your periods can sometimes make you wonder whether your thyroid is involved.
The thyroid is a small, butterfly-shaped gland at the front of the neck, but the hormones it produces affect almost every part of the body. Thyroid hormones help regulate how the body uses energy and influence processes involving the heart, brain, muscles, digestion and body temperature.
When the thyroid produces too little hormone, the condition is called hypothyroidism, or an underactive thyroid. When it produces too much thyroid hormone, it is called hyperthyroidism, or an overactive thyroid.
Thyroid problems can develop gradually, and many of their symptoms are also caused by other conditions. That is why symptoms alone cannot confirm a thyroid disorder. Blood tests, particularly a TSH test, are commonly used to evaluate thyroid function.
This guide explains the most common thyroid problems, their symptoms and causes, how thyroid tests work, available treatments, and when it is important to seek medical care.
What Is the Thyroid and What Does It Do?
The thyroid is an endocrine gland located in the lower front part of the neck.
Its main job is to produce thyroid hormones, particularly:
- T4 (thyroxine)
- T3 (triiodothyronine)
T4 is the major hormone produced by the thyroid. Some T4 is converted into T3 in tissues around the body, and T3 is the more active thyroid hormone at the cellular level.
The thyroid is regulated by the brain through the pituitary gland. The pituitary produces thyroid-stimulating hormone (TSH), which tells the thyroid how much thyroid hormone to produce.
A simple way to understand this system is to think of the pituitary as a thermostat and the thyroid as the heating system.
When thyroid hormone levels are too low, the pituitary generally increases TSH to stimulate the thyroid. When thyroid hormone levels are high, TSH usually decreases.
This relationship is why TSH is such an important starting point when doctors evaluate possible thyroid problems.
What Are the Main Types of Thyroid Problems?
There are several thyroid disorders, but two of the most common functional thyroid problems are:
1. Hypothyroidism
Hypothyroidism occurs when the thyroid does not produce enough thyroid hormone.
Because thyroid hormones help regulate the body’s energy use, too little hormone can cause many body processes to slow down.
Common symptoms include:
- Fatigue
- Weight gain
- Feeling unusually cold
- Constipation
- Dry skin
- Dry or thinning hair
- Muscle or joint aches
- Slower heart rate
- Depression or low mood
- Heavy or irregular menstrual periods
- Fertility problems
Symptoms can develop gradually, sometimes making the condition difficult to recognize at first.
2. Hyperthyroidism
Hyperthyroidism occurs when the thyroid produces too much thyroid hormone.
Instead of slowing body processes, excess thyroid hormone can make many systems work faster.
Possible symptoms include:
- Unexplained weight loss
- Feeling unusually hot
- Excessive sweating
- Rapid or irregular heartbeat
- Trembling
- Anxiety or irritability
- Difficulty sleeping
- Muscle weakness
- Frequent bowel movements or diarrhea
- Increased appetite
- Hair thinning
- Menstrual changes
Not everyone experiences all of these symptoms.
Other Thyroid Problems
Thyroid disorders can also include:
- Thyroiditis — inflammation of the thyroid
- Hashimoto’s disease — an autoimmune condition that commonly causes hypothyroidism
- Graves’ disease — an autoimmune condition that commonly causes hyperthyroidism
- Goiter — enlargement of the thyroid gland
- Thyroid nodules — lumps within the thyroid
- Thyroid problems caused by certain medications or previous thyroid treatment
Some conditions can temporarily cause the thyroid to release excess hormone and later become underactive. Thyroiditis is one example.
12 Common Signs and Symptoms of Thyroid Problems
Thyroid symptoms vary depending on whether the thyroid is underactive, overactive, inflamed, enlarged or affected by another disorder.
Here are some of the most important symptoms to recognize.
1. Unexplained Fatigue
Persistent tiredness is one of the symptoms commonly associated with hypothyroidism.
You may feel exhausted even after getting enough sleep or notice that everyday activities require more effort than usual.
However, fatigue is extremely common and can also occur with anemia, sleep problems, infections, stress, depression, nutritional deficiencies and many other conditions.
Fatigue alone does not mean you have a thyroid problem.
2. Unexplained Weight Gain or Weight Loss
Changes in thyroid hormone levels can influence metabolism and body weight.
An underactive thyroid may contribute to weight gain, while an overactive thyroid may cause weight loss, sometimes despite having an increased appetite.
But thyroid problems are not the only explanation for changes in weight.
Diet, physical activity, medications, sleep, stress, menopause, pregnancy, insulin resistance and numerous medical conditions can also affect body weight.
3. Feeling Unusually Cold
Feeling colder than people around you can occur with hypothyroidism.
A person with an underactive thyroid may have increased sensitivity to cold because thyroid hormones influence the body’s energy use and heat production.
If you are persistently cold, however, thyroid disease is only one possible explanation.
4. Feeling Unusually Hot or Sweating More
The opposite pattern may occur with hyperthyroidism.
An overactive thyroid can make you more sensitive to heat and cause increased sweating or warm skin.
5. Hair Thinning or Hair Loss
Changes in thyroid hormone levels can affect the hair-growth cycle.
Hypothyroidism may be associated with dry, thinning hair, while hyperthyroidism can also cause hair thinning or loss.
Hair loss is not specific to thyroid disease, though. Iron deficiency, nutritional deficiencies, hormonal changes, stress, genetics, certain medications and other medical conditions can also cause it.
6. Dry Skin
Dry or rough skin can occur with hypothyroidism.
Some people may also notice that their skin feels less soft than usual or becomes unusually dry despite their normal skincare routine.
Again, dry skin alone is not enough to diagnose thyroid disease.
7. Changes in Heart Rate or Palpitations
An underactive thyroid can be associated with a slower heart rate.
Hyperthyroidism, on the other hand, may cause a fast or irregular heartbeat or noticeable palpitations.
A new, persistent or severe racing heartbeat deserves medical evaluation, particularly if it occurs with chest pain, fainting, severe shortness of breath or significant dizziness.
8. Anxiety, Irritability or Mood Changes
An overactive thyroid may contribute to:
- Nervousness
- Anxiety
- Irritability
- Restlessness
- Mood changes
- Difficulty sleeping
Hypothyroidism can instead be associated with depression or low mood.
Because mental health symptoms have many possible causes, thyroid testing may sometimes be considered when symptoms occur alongside other signs of thyroid dysfunction.
9. Constipation or More Frequent Bowel Movements
An underactive thyroid may slow digestion and contribute to constipation.
An overactive thyroid can have the opposite effect and may cause more frequent bowel movements or diarrhea.
10. Menstrual Changes and Fertility Problems
Thyroid disorders can affect reproductive health.
Hypothyroidism may be associated with heavy or irregular menstrual periods and fertility difficulties. Thyroid dysfunction can also interfere with ovulation.
Hyperthyroidism can also affect menstrual patterns and fertility.
For people having difficulty becoming pregnant, thyroid testing may be part of the medical evaluation when clinically appropriate.
11. Muscle Weakness, Aches or Trembling
Thyroid dysfunction can affect muscles.
Hypothyroidism may be associated with muscle aches and joint pain, while hyperthyroidism can cause muscle weakness and trembling.
If weakness is sudden or severe, it should not automatically be attributed to the thyroid and may require urgent evaluation.
12. Swelling or a Lump in the Neck
An enlarged thyroid is called a goiter.
A goiter may appear as swelling at the front of the neck. Thyroid nodules can also create a lump or fullness.
A neck lump does not automatically mean thyroid cancer. Many thyroid nodules are benign, but a new or enlarging thyroid or neck lump should be assessed by a healthcare professional.
Difficulty swallowing or breathing because of neck swelling requires prompt medical attention.
What Causes Thyroid Problems?
There is no single cause of thyroid disease.
The underlying cause depends on whether the thyroid is underactive, overactive, inflamed, enlarged or affected by another condition.
Hashimoto’s Disease
Hashimoto’s disease is an autoimmune disorder and one of the most common causes of hypothyroidism.
In autoimmune disease, the immune system mistakenly attacks the body’s own tissues.
With Hashimoto’s disease, the immune system damages thyroid tissue over time, reducing its ability to produce enough thyroid hormone.
Some people initially have few or no symptoms, while others eventually develop typical hypothyroidism symptoms.
Graves’ Disease
Graves’ disease is an autoimmune disorder that commonly causes hyperthyroidism.
The immune system produces antibodies that stimulate the thyroid to produce too much thyroid hormone.
Graves’ disease can also cause eye-related problems in some people, including irritation, redness, swelling or changes in vision.
Thyroiditis
Thyroiditis means inflammation of the thyroid.
Depending on the type, thyroiditis may cause thyroid hormone to leak into the bloodstream, temporarily producing symptoms of excess thyroid hormone.
Later, thyroid hormone levels may become low.
Some forms include:
- Subacute thyroiditis
- Postpartum thyroiditis
- Painless or silent thyroiditis
Some people recover normal thyroid function, while others develop longer-term hypothyroidism.
Previous Thyroid Surgery or Radiation
Removing part or all of the thyroid can reduce hormone production.
Radioactive iodine treatment for hyperthyroidism also intentionally reduces thyroid activity. Many people who receive this treatment eventually develop hypothyroidism and need thyroid hormone replacement.
Radiation involving the neck can also affect thyroid function.
Certain Medicines
Some medications can interfere with thyroid function.
The specific medicines involved depend on the condition being treated and may include certain heart, psychiatric and cancer medicines.
This is one reason it is important to tell your healthcare professional about every prescription medicine, over-the-counter medication and supplement you take.
Iodine Imbalance
The thyroid needs iodine to produce thyroid hormones.
Both insufficient and excessive iodine can affect thyroid function in certain circumstances.
However, taking extra iodine does not automatically improve thyroid health. In some people with autoimmune thyroid disease, large amounts of iodine can worsen thyroid dysfunction.
Do not start high-dose iodine or seaweed-based supplements simply because you suspect a thyroid problem.
Thyroid Problems in Women
Thyroid disease can affect women of all ages.
Women are more likely than men to develop some thyroid disorders, particularly autoimmune thyroid conditions.
Thyroid dysfunction may affect:
- Menstrual cycles
- Ovulation
- Fertility
- Pregnancy
- Energy levels
- Weight
- Hair and skin
- Mood
- Temperature tolerance
Pregnancy is also a time when thyroid function may require particular attention.
Untreated hypothyroidism during pregnancy can cause complications, while people already taking thyroid hormone medication may need their dose adjusted during pregnancy.
If you are pregnant, planning pregnancy or having fertility difficulties, discuss thyroid testing with your healthcare professional rather than trying to interpret symptoms yourself.
Thyroid Problems in Men
Thyroid disorders can affect men as well.
Possible symptoms include:
- Fatigue
- Weight changes
- Temperature sensitivity
- Hair changes
- Mood changes
- Constipation or bowel changes
- Muscle weakness
- Changes in heart rate
- Reduced sexual interest
- Fertility problems
Because these symptoms overlap with many other conditions, testing is important when thyroid disease is suspected.
How Are Thyroid Problems Diagnosed?
Symptoms can raise suspicion, but symptoms alone cannot diagnose thyroid disease.
A healthcare professional may consider:
- Your symptoms
- Medical and family history
- Physical examination
- Thyroid blood tests
- Thyroid antibody testing when appropriate
- Ultrasound or other imaging when indicated
- Additional testing depending on the suspected cause
The exact tests depend on what your healthcare professional is trying to determine.
What Is a TSH Test?
TSH stands for thyroid-stimulating hormone.
It is commonly the first blood test used to evaluate thyroid function.
In primary hypothyroidism, TSH is typically elevated because the pituitary is trying to stimulate an underactive thyroid.
In hyperthyroidism, TSH is usually low because the body is responding to excessive thyroid hormone.
However, TSH results must be interpreted in context. A low TSH can occasionally occur for reasons other than primary hyperthyroidism, including certain pituitary disorders or medication-related factors.
What Do Free T4 and T3 Tests Show?
Free T4
Free T4 measures the unbound form of thyroxine available to enter tissues.
TSH and free T4 are commonly interpreted together.
For example:
- High TSH + low free T4 commonly indicates primary hypothyroidism.
- Low TSH + high free T4 commonly indicates hyperthyroidism.
- Low TSH + low free T4 can suggest a problem involving the pituitary rather than the thyroid itself.
These patterns are simplified examples. A healthcare professional must interpret results according to the individual situation, laboratory reference ranges and other clinical information.
T3
T3 testing can be particularly useful when hyperthyroidism is suspected.
In some people with a low TSH, T3 may be elevated even when free T4 is still within the normal range.
T3 is generally less useful for diagnosing hypothyroidism because it can remain normal even when someone has significant hypothyroidism.
What Are Thyroid Antibody Tests?
Thyroid antibody tests can help identify certain autoimmune thyroid diseases.
Depending on the suspected condition, a healthcare professional may order tests such as:
- TPO antibodies
- TSI
- TRAb
- Other thyroid antibodies when clinically appropriate
For example, TPO antibodies can support a diagnosis of Hashimoto’s disease in the appropriate clinical setting.
Not everyone with thyroid symptoms needs every antibody test.
Can Supplements Affect Thyroid Blood Tests?
Yes.
Some supplements can interfere with laboratory testing.
One important example is biotin, which is found in many hair, skin and nail supplements.
Biotin can interfere with some thyroid laboratory measurements and make results appear abnormal when they do not accurately reflect thyroid function.
The American Thyroid Association advises discussing biotin use with your healthcare professional and notes that biotin should generally be stopped for two days before thyroid blood testing to avoid this interference. Follow the instructions provided by your own healthcare professional or laboratory.
Always tell your healthcare professional about supplements before thyroid testing.
Thyroid Ultrasound and Other Tests
A thyroid ultrasound may be recommended when a healthcare professional needs to evaluate:
- A thyroid lump
- Thyroid enlargement
- Nodules
- Certain structural abnormalities
Ultrasound looks at the structure of the thyroid rather than simply measuring thyroid hormone levels.
Other tests, including specialized scans or radioactive iodine uptake testing, may be used in selected cases, particularly when doctors need to determine the cause of hyperthyroidism.
Not every person with thyroid symptoms needs imaging.
How Are Thyroid Problems Treated?
Treatment depends entirely on the type and cause of the thyroid disorder.
There is no single treatment that is appropriate for every thyroid problem.
Treatment for Hypothyroidism
The standard treatment for persistent hypothyroidism is levothyroxine, a medication that replaces the thyroid hormone the body is no longer producing adequately.
The dose is individualized.
After starting treatment or changing the dose, blood testing is generally repeated after several weeks to determine whether the dose needs adjustment. NIDDK notes that a blood test is commonly performed about 6–8 weeks after starting or adjusting levothyroxine.
Once the appropriate dose is established, ongoing monitoring is still important.
Do not stop or change thyroid medication without discussing it with your healthcare professional.
Taking too much thyroid hormone can also cause problems, including abnormal heart rhythms and bone loss over time.
Treatment for Hyperthyroidism
Treatment depends on the cause, severity, age, other health conditions and whether pregnancy is involved.
Common treatment approaches include:
Antithyroid medicines
These medicines reduce thyroid hormone production.
Methimazole is commonly used, while propylthiouracil may be preferred in particular circumstances, including certain stages of pregnancy.
Beta-blockers
Beta-blockers may be used to reduce symptoms such as:
- Rapid heartbeat
- Trembling
- Nervousness
They help control symptoms but do not correct the underlying excess production of thyroid hormone.
Radioactive iodine
Radioiodine can reduce thyroid hormone production by destroying thyroid cells that take up iodine.
It is not appropriate during pregnancy or breastfeeding because radioactive iodine can affect the baby’s thyroid.
Surgery
Some people with hyperthyroidism or other thyroid conditions may need surgery to remove part or all of the thyroid.
The choice depends on the individual condition and clinical circumstances.
Can Thyroid Problems Be Cured?
That depends on the specific thyroid disorder.
Some thyroid conditions are temporary.
For example, certain forms of thyroiditis can cause temporary changes in thyroid hormone levels before thyroid function returns toward normal.
Other conditions are long-term.
Hashimoto’s disease can lead to permanent hypothyroidism requiring ongoing thyroid hormone replacement.
After some treatments for hyperthyroidism, such as radioactive iodine or complete thyroid removal, hypothyroidism may occur and require lifelong hormone replacement.
The goal of treatment is not always to “cure” the thyroid itself. In many cases, the goal is to restore or maintain normal hormone levels and prevent complications.
Can Thyroid Problems Cause Weight Gain?
Yes, particularly hypothyroidism.
An underactive thyroid can contribute to weight gain because thyroid hormones influence how the body uses energy.
However, thyroid disease is rarely the only possible explanation for weight change.
If weight gain is accompanied by fatigue, cold intolerance, constipation, dry skin, hair changes or menstrual changes, discussing thyroid testing with a healthcare professional may be reasonable.
If thyroid testing is normal, continuing to blame the thyroid can delay investigation of other causes.
Can Thyroid Problems Cause Hair Loss?
Yes.
Both underactive and overactive thyroid disorders can be associated with hair thinning or loss.
But hair loss has many possible causes, including:
- Iron deficiency
- Nutritional deficiencies
- Hormonal changes
- Stress
- Genetics
- Certain medications
- Scalp disorders
- Recent illness
If hair loss is persistent, sudden or significant, it is worth discussing with a healthcare professional rather than assuming the thyroid is responsible.
Can Thyroid Problems Affect Periods?
Yes.
Thyroid dysfunction can affect menstrual patterns.
Hypothyroidism may contribute to heavy or irregular periods, while thyroid dysfunction more broadly can interfere with ovulation and fertility.
If your periods have suddenly become much heavier, significantly more irregular or consistently different from your usual pattern, thyroid disease is one possibility—but not the only one.
When Should You Get Your Thyroid Checked?
Consider discussing thyroid testing with a healthcare professional if you have persistent or unexplained symptoms such as:
- Ongoing fatigue
- Unexplained weight changes
- Significant cold or heat intolerance
- Persistent constipation or diarrhea
- Hair thinning
- Dry skin
- Menstrual changes
- Fertility difficulties
- Persistent anxiety or low mood alongside other symptoms
- Palpitations or changes in heart rate
- Neck swelling or a thyroid lump
- A family history of thyroid disease
You may also need thyroid evaluation if you have certain autoimmune conditions, previous thyroid disease or a history of thyroid treatment.
A healthcare professional can decide which tests are appropriate rather than relying on symptoms alone.
When Is a Thyroid Problem an Emergency?
Most thyroid symptoms are not emergencies, but certain situations require urgent medical attention.
Seek urgent medical care for symptoms such as:
- Severe difficulty breathing
- Significant difficulty swallowing caused by neck swelling
- Severe chest pain
- Fainting
- Severe or rapidly worsening shortness of breath
- A very rapid or irregular heartbeat accompanied by severe symptoms
- Severe confusion or reduced consciousness
Rare but serious thyroid-related emergencies can occur, including severe untreated hypothyroidism and severe hyperthyroidism.
For example, myxedema coma is a rare, life-threatening complication of severe hypothyroidism requiring immediate treatment.
Thyroid Problems: What You Should Remember
Thyroid problems can affect much more than the neck.
Because thyroid hormones influence energy use and multiple body systems, thyroid dysfunction may appear through changes in:
- Energy
- Weight
- Body temperature
- Heart rate
- Digestion
- Hair and skin
- Mood
- Menstrual cycles
- Fertility
- Muscle function
The two major patterns are hypothyroidism, where thyroid hormone production is too low, and hyperthyroidism, where thyroid hormone levels are too high.
But many thyroid symptoms overlap with other health conditions.
The most important point is that symptoms alone cannot tell you whether you have a thyroid disorder. A healthcare professional can evaluate your symptoms and use appropriate blood tests—often beginning with TSH—to determine whether further investigation is needed.
Frequently Asked Questions About Thyroid Problems
Common symptoms can include fatigue, unexplained weight changes, cold or heat intolerance, hair changes, dry skin, mood changes, constipation or diarrhea, menstrual changes and changes in heart rate. Symptoms differ depending on whether the thyroid is underactive or overactive.
Early thyroid problems may cause subtle symptoms such as fatigue, changes in weight, feeling unusually cold or hot, changes in bowel habits, hair thinning or menstrual changes. However, these symptoms are not specific to thyroid disease and require appropriate testing for diagnosis.
You cannot reliably diagnose a thyroid disorder based on symptoms alone. A healthcare professional may evaluate your symptoms and medical history and order thyroid blood tests, commonly starting with a TSH test.
A high TSH commonly indicates that the thyroid is not producing enough thyroid hormone, particularly when free T4 is low. This pattern is typical of primary hypothyroidism, but test results must always be interpreted in context.
A low TSH commonly occurs when the body has too much thyroid hormone, as in hyperthyroidism. However, a low TSH can have other causes, so additional testing may be needed to understand the result.
Yes. Hypothyroidism can contribute to weight gain. However, weight gain has many possible causes, so thyroid disease should not be assumed without appropriate evaluation.
Yes. Thyroid dysfunction can contribute to menstrual changes and fertility problems. People experiencing difficulty becoming pregnant may be evaluated for thyroid problems when clinically appropriate.
Yes. Treatment depends on the specific thyroid disorder. Hypothyroidism is commonly treated with levothyroxine, while hyperthyroidism may be treated with medication, radioactive iodine or surgery depending on the cause and individual circumstances.
Conclusion
Thyroid problems are common and can affect many aspects of health, from energy and weight to heart rate, digestion, hair, skin, menstrual cycles and fertility.
An underactive thyroid can cause symptoms such as fatigue, weight gain and cold intolerance, while an overactive thyroid can cause weight loss, heat intolerance, sweating, anxiety and a fast heartbeat.
But thyroid symptoms are not unique to thyroid disease.
If you have persistent or unexplained symptoms, the most useful next step is not to guess from a symptom checklist or start supplements on your own. A healthcare professional can determine whether thyroid testing is appropriate and interpret the results in the context of your overall health.
When a thyroid disorder is identified, effective treatments are available for most conditions.
Medical Disclaimer
This article is for educational and informational purposes only and is not a substitute for professional medical advice, diagnosis or treatment.
Thyroid symptoms can overlap with many other medical conditions. Do not diagnose yourself or start, stop or change thyroid medication or supplements based solely on information in this article.
If you have persistent symptoms, abnormal thyroid test results, pregnancy-related concerns, fertility concerns, a new neck lump, difficulty breathing or swallowing, or severe or rapidly worsening symptoms, speak with a qualified healthcare professional.
Sources & References
- National Institute of Diabetes and Digestive and Kidney Diseases — Hypothyroidism
- National Institute of Diabetes and Digestive and Kidney Diseases — Hyperthyroidism
- American Thyroid Association — Thyroid Function Tests
- American Thyroid Association — How to Order Thyroid Function Tests
- NIDDK — Hashimoto’s Disease
- NIDDK — Graves’ Disease
- NHS — Overactive Thyroid (Hyperthyroidism)